Typical applicators for dispensing adhesive may include positive displacement fluid dispensers that intermittently apply a flow of adhesive to a substrate. The fluid dispensers actuate between an on cycle, during which adhesive is flowing through a nozzle of the dispenser, and an off cycle, during which adhesive is prevented from flowing through the nozzle of the dispenser. During the off cycle, unused adhesive builds up within the applicator, which leads to elevated pressures within the applicator. Upon commencing the next on cycle, the built-up adhesive within the applicator causes the adhesive to exit the dispenser nozzle at an inconsistent flow rate or a flow rate that is different than intended. This leads to adhesive pattern deformation on the substrate.
To remedy this issue, some applicators include not only supply channels but also recirculation channels that redirect unused adhesive back to the inlet of the pump assemblies within the applicator during the fluid dispenser off cycle, or alternatively back to the adhesive tank that supplies the adhesive to the applicator. Though the recirculation channel may redirect unused adhesive, the recirculation channel alone does not completely prevent pressure build-up within the applicator. When adhesive flows through the recirculation channel during a fluid dispenser off cycle, the adhesive flows at a pressure that is different than the pressure of the adhesive in the applicator supply channel that provides the pump assemblies within the applicator with adhesive from the adhesive tank. This pressure differential, which is a function of the unregulated pressures of the recirculation channels and the applicator supply channels, also cause the issues noted above in relation to an applicator that does not have a recirculation channel.
Therefore, there is a need for an applicator for dispensing adhesive that allows for active management and control of the adhesive pressure differential that exists between the recirculation channel and the applicator supply channels.